textproduct: Quad Cities

KEY MESSAGES

- Widespread soaking rainfall is expected today through Saturday with an 80-100% chance of rainfall amounts over 1 inch and a 40-70% chance of rainfall amounts over 2 inches. A Slight Risk (level 2 of 4) for localized flash flooding is in effect area-wide.

- A conditional risk (level 1 of 5) for severe thunderstorms is in effect this afternoon into the evening for areas south of Highway 20. The primary threat with any storms will be isolated damaging winds. Isolated tornadoes are possible in southeast Iowa and northeast Missouri.

SHORT TERM /THROUGH SATURDAY NIGHT/

Issued at 259 AM CDT Fri Jul 31 2026

A day of on-and-off rain is in store for the area today as a seasonably strong shortwave trough intensifies and moves through the area. Early this morning, cyclogenesis has supported the development of a surface low along the NE-SD-IA border. In the warm sector, advection along the warm conveyor belt has supported moisture transport into Missouri and Iowa with PWATs of 2.0+ inches. While this is rather anomalous at well above 1.7 inches, the 90th percentile, it is not out of the question given upstream PWATs of 2.39 inches sampled in KOAX's 31/00Z sounding. With this increasing moisture and synoptic uplift along the eastern side of this intensifying cyclone, a widespread rain event is expected today through Saturday.

While rain is expected throughout much of the day, dry periods are expected between multiple rounds of showers and storms. While some showers are moving through the area now, the main line, which is currently a weakening MCS stretching from northeast Kansas into central Iowa, will reach eastern Iowa around daybreak. Showers are expected area-wide as it moves eastward, and parts of southeast Iowa and northeast Missouri may see embedded thunderstorms due to MLCAPE up to 500 J/kg. By early afternoon, this line of showers and storms will push through western Illinois, allowing for dry periods and potentially some clearing across eastern Iowa and northeast Missouri.

Additional showers and storms, including some strong to severe, are possible this afternoon through the evening. Any clearing that occurs, coupled with continued WAA in the warm sector, will lead to increased instability through the low levels, with much of the guidance showing MLCAPE of 1000-1500 J/kg. Deep layer shear is more supportive of a severe risk, with 25-35 kts through much of the area. The primary threats with any strong to severe storms will be isolated damaging winds due to strong winds aloft. A secondary threat in the vicinity of the low across southeast Iowa and northeast Missouri is an isolated tornado or landspout, as stronger low-level shear (0-3 km SRH of 200-300) and veering profiles in the vicinity of the low and cold front will be supportive of low-topped supercells. Given these threats, SPC has issued a conditional Marginal (level 1 of 5) risk for areas south of Highway 20 and a Slight (level 2 of 5) for the far southern reaches of the area into eastern Missouri and western Illinois.

Scattered showers will continue overnight through Saturday afternoon as the low slowly works its way southeastward. Total rainfall accumulations through Saturday of 1-3 inches are expected, with the NBM having an 80-100% chance of exceeding 1 inch area-wide. Some areas, particularly those in southeast Iowa and northeast Missouri, have lower chances of exceeding 2 inches, leading to a 40-70% southwest-to-northeast gradient of 2 inch exceedance probabilities. Some guidance suggests that locally higher amounts of 3-5 inches may also be possible. This will be quite welcome due to recent dryness, which in turn will help reduce flooding risks. The greatest chance for any flooding will be if slow-moving heavy rainfall repeatedly moves over urban areas or areas with poor drainage. Due to this, WPC has issued a Slight (level 2 of 4) risk for flash flooding area-wide today.

As showers end on Saturday afternoon, a strong pressure gradient on the backside of the low will induce gusty northerly winds up to 30 mph that last through late evening.

LONG TERM /SUNDAY THROUGH THURSDAY/

Issued at 259 AM CDT Fri Jul 31 2026

The upper-level trough that will help bring precipitation across the area today and Saturday will finally depart the region to the east Sunday, leading to a period of dry conditions. Surface high pressure building across the area, along with upper-level ridging over the Intermountain West region protruding from a large upper-level high over the southwestern CONUS, will support more quiescent conditions through Tuesday, with seasonal temperatures (highs in the lower 80s) for Sunday through Tuesday.

In terms of active weather, it appears mainly Wednesday/Thursday will be the time to watch as the upper-level ridging breaks down, allowing a mid-level trough to approach the region. An attendant surface cold front is also progged to accompany the trough, although there are significant timing differences among the global models of the front, and thus, timing of precipitation with that boundary. Severe weather potential with this front appears to be pretty low at this time, given modest values of instability and shear (25-35 knots for 0-6 km shear magnitudes). The various machine learning severe weather probability guidance supports the more limited severe weather signal.

AVIATION /18Z TAFS THROUGH 18Z SATURDAY/

Issued at 1212 PM CDT Fri Jul 31 2026

A messy aviation forecast is ahead of us, as we have a slow- moving storm system pass through the area over the next 24 hours. We currently are watching the shield of widespread rainfall move out of the area, which has brought IFR vis/cigs to much of the area this morning. For the remainder of the afternoon, a broken-overcast deck will remain, with cigs around 1000-2000 ft. Isolated-scattered showers will pass through the area between 18-21z, with increasing chances and coverage of thunderstorms after 21z. With any shower/storm, lower cigs and vis can be expected. We can see cigs drop to as low as 500 ft or lower, especially at CID/DBQ after 00z this evening, with vis between 2-5 SM. At MLI/BRL, cigs may drop as low as 500-1000 ft in thunderstorms with vis of 3-5 SM. These conditions will continue well into the night and through Saturday morning, with flight conditions not improving for many until at least 18z Saturday. Frequent lightning and gusty winds can be expected at terminals with any thunderstorm, with heavy rainfall possibly dropping vis lower than currently advertised.

With the surface low tracking overhead through the TAF period, winds will be quite variable, especially between 00-12z. Ahead of the surface low, winds will largely be out of the south/southeast, becoming northeasterly on the backside around 08z and beyond. Wind speeds will increase quite a bit on the backside of the system, with gusts upwards to 25-30 KTs out of the northeast by 12z Saturday for most of the area. Largely light (5-10 KTs) and variable winds can be expected under the surface low.

DVN WATCHES/WARNINGS/ADVISORIES

IA...None. IL...None. MO...None.